[Lab 3.4] tcpdump stays empty

thomas.bucaioni

Hello,
Here is the setting:

$ kubectl get endpoints nginx 
NAME    ENDPOINTS                                           AGE
nginx   192.168.19.4:80,192.168.86.67:80,192.168.86.69:80   25m
$ kubectl get service nginx 
NAME    TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
nginx   ClusterIP   10.100.200.161   <none>        80/TCP    27m
$ curl 10.100.200.161:80

Then the curl command sometimes shows the Nginx welcome page, sometimes not. But the tcpdump stays blank. Anything wrong? Both worker and cp are running tcpdump on the tunnel and see nothing:

sudo tcpdump -i tunl0

chrispokorni

Hi @thomas.bucaioni,

The concerning behavior of the nginx service is the "sometimes not" showing the nginx welcome page. This symptom typically indicates that the nodes are not networked together to Kubernetes' liking. Assuming the nodes are on the same network, this may be a firewall issues, if it blocks required protocols to various ports. Not opening the firewall to all traffic from all sources, all protocols, and to all port destinations as described in the set up videos may cause these types of issues. Are all the control plane pods running? What is the output of

kubectl get pods -A

Regards,
-Chris

thomas.bucaioni

Hi @chrispokorni
It could well be my firewall, it's custom... The output of kubectl get pods -A is:

$ kubectl get pods -A
NAMESPACE     NAME                                       READY   STATUS    RESTARTS     AGE
default       nginx-74d589986c-4ncr8                     1/1     Running   1 (6d ago)   6d1h
default       nginx-74d589986c-bwfkk                     1/1     Running   1 (6d ago)   6d2h
default       nginx-74d589986c-l5p5p                     1/1     Running   1 (6d ago)   6d2h
kube-system   calico-kube-controllers-56fcbf9d6b-bnvxg   1/1     Running   1 (6d ago)   6d4h
kube-system   calico-node-gfrl4                          0/1     Running   1 (6d ago)   6d4h
kube-system   calico-node-rn8pb                          0/1     Running   1            6d4h
kube-system   coredns-64897985d-9wzkz                    1/1     Running   1 (6d ago)   6d6h
kube-system   coredns-64897985d-ff8r8                    1/1     Running   1 (6d ago)   6d6h
kube-system   etcd-dl-dt-03                              1/1     Running   6 (6d ago)   6d6h
kube-system   kube-apiserver-dl-dt-03                    1/1     Running   7 (6d ago)   6d6h
kube-system   kube-controller-manager-dl-dt-03           1/1     Running   6 (6d ago)   6d6h
kube-system   kube-proxy-dc2dn                           1/1     Running   2 (6d ago)   6d6h
kube-system   kube-proxy-tkhfr                           1/1     Running   2 (6d ago)   6d6h
kube-system   kube-scheduler-dl-dt-03                    1/1     Running   6 (6d ago)   6d6h

Otherwise, here is my firewall:

$ cat bin/firewall.sh
#!/bin/sh
#
# firewall.sh
 
# WAN and LAN interfaces
IFACE_LAN=enp2s0
IFACE_WAN=enp0s29f7u7
IFACE_LAN_IP=172.168.1.0/24
 
# Accept all
iptables -t filter -P INPUT ACCEPT
iptables -t filter -P FORWARD ACCEPT
iptables -t filter -P OUTPUT ACCEPT
iptables -t nat -P INPUT ACCEPT
iptables -t nat -P PREROUTING ACCEPT
iptables -t nat -P POSTROUTING ACCEPT
iptables -t nat -P OUTPUT ACCEPT
iptables -t mangle -P INPUT ACCEPT
iptables -t mangle -P PREROUTING ACCEPT
iptables -t mangle -P FORWARD ACCEPT
iptables -t mangle -P POSTROUTING ACCEPT
iptables -t mangle -P OUTPUT ACCEPT
 
# Reset the counters
iptables -t filter -Z
iptables -t nat -Z
iptables -t mangle -Z
 
# Delete all active rules and personalized chains
iptables -t filter -F
iptables -t filter -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X
 
# Default policy
iptables -P INPUT DROP
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
 
# Trust ourselves
iptables -A INPUT -i lo -j ACCEPT
#iptables -A INPUT -i lo --dport 6443 -j ACCEPT
#iptables -A INPUT -i lo --sport 6443 -j ACCEPT
 
# Ping
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A INPUT -p icmp --icmp-type time-exceeded -j ACCEPT
iptables -A INPUT -p icmp --icmp-type destination-unreachable -j ACCEPT
 
# Established connections
iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT
 
# SSH
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 22 -j ACCEPT
#iptables -A INPUT -p tcp -i $IFACE_WAN --dport 22 -j ACCEPT
 
#iptables -A INPUT -p tcp -i $IFACE_WAN --sport 3000 -j ACCEPT
#iptables -A INPUT -p tcp -i $IFACE_WAN --dport 3000 -j ACCEPT
#iptables -A INPUT -p tcp -i $IFACE_LAN --dport 3000 -j ACCEPT
#iptables -A INPUT -p tcp -i $IFACE_LAN --sport 3000 -j ACCEPT
 
#iptables -A INPUT -p udp -i $IFACE_WAN --sport 3000 -j ACCEPT
#iptables -A INPUT -p udp -i $IFACE_WAN --dport 3000 -j ACCEPT
#iptables -A INPUT -p udp -i $IFACE_LAN --dport 3000 -j ACCEPT
#iptables -A INPUT -p udp -i $IFACE_LAN --sport 3000 -j ACCEPT
 
# Kubernetes
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 6443 -j ACCEPT
iptables -A INPUT -p udp -i $IFACE_LAN --dport 6443 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --sport 6443 -j ACCEPT
iptables -A INPUT -p udp -i $IFACE_LAN --sport 6443 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 6449 -j ACCEPT
iptables -A INPUT -p udp -i $IFACE_LAN --dport 6449 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --sport 6449 -j ACCEPT
iptables -A INPUT -p udp -i $IFACE_LAN --sport 6449 -j ACCEPT
 
# Dnsmasq
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 53 -j ACCEPT
iptables -A INPUT -p udp -i $IFACE_LAN --dport 53 -j ACCEPT
iptables -A INPUT -p udp -i $IFACE_LAN --dport 67:68 -j ACCEPT
 
# TCP
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_WAN --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 443 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_WAN --dport 443 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --sport 80 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_WAN --sport 80 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --sport 443 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_WAN --sport 443 -j ACCEPT
 
# Packet forwarding activation
iptables -t nat -A POSTROUTING -o $IFACE_WAN -s $IFACE_LAN_IP -j MASQUERADE
sysctl -q -w net.ipv4.ip_forward=1
 
# NFS
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 2049 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --sport 2049 -j ACCEPT
 
# Samba
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 445 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --sport 445 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --dport 139 -j ACCEPT
iptables -A INPUT -p tcp -i $IFACE_LAN --sport 139 -j ACCEPT
 
# NTP
iptables -A INPUT -p udp -i $IFACE_LAN --dport 123 -j ACCEPT
 
# Log refused packets
iptables -A INPUT -m limit --limit 2/min -j LOG --log-prefix "IPv4 packet rejected ++ "
iptables -A INPUT -j DROP
 
# Save the configuration
service iptables save

thomas.bucaioni

Even after flushing the firewall, curl doesn't reach all the nodes:

systemctl stop iptables
systemctl disable iptables
systemctl status iptables
iptables --flush
service iptables save
cat  /etc/sysconfig/iptables

thomas.bucaioni

The CP is on a router connected to a box on one interface, and to the workers on the other interface.
But the box seems to be in 192.168.x.x, which could interfere with calico?
If I set up the calico configuration to 182.168.x.x, maybe it goes well

thomas.bucaioni

Even after changing the calico configuration to:

apiVersion: kubeadm.k8s.io/v1beta2
kind: ClusterConfiguration
kubernetesVersion: 1.22.1
controlPlaneEndpoint: "k8scp:6443"
networking:
  podSubnet: 182.168.0.0/16

the join command proposed is:

kubeadm join 192.168.1.194:6443 --token v9ii23.bz2vgnyxttimr3tu --discovery-token-ca-cert-hash sha256:5c5c0dd3cd3e2a75a27f119cd637ee82fac7b9febb7671cf5272c16d465683ab

thomas.bucaioni

My router has a name already, dl-dt-03, so I guess during the install I need to replace all the k8scp with the name of the router?

thomas.bucaioni

So, I've put the worker node on the router and the cp node on the former worker node. Now the service has no endpoint:

$ kubectl get ep nginx 
NAME    ENDPOINTS   AGE
nginx   <none>      9m35s

Apparently, some pods are frozen:

$ kubectl get pods -A
NAMESPACE     NAME                                      READY   STATUS              RESTARTS   AGE
default       nginx-74d589986c-zpc74                    0/1     ContainerCreating   0          13m
default       nginx-85b98978db-frgdh                    0/1     ContainerCreating   0          20m
kube-system   calico-kube-controllers-7c845d499-9l9x9   1/1     Running             0          42m
kube-system   calico-node-xgz2k                         1/1     Running             0          42m
kube-system   calico-node-xwvl6                         0/1     Init:0/3            0          37m
kube-system   coredns-64897985d-hjn7c                   1/1     Running             0          44m
kube-system   coredns-64897985d-zgxqp                   1/1     Running             0          44m
kube-system   etcd-hp-tw-01                             1/1     Running             0          45m
kube-system   kube-apiserver-hp-tw-01                   1/1     Running             0          45m
kube-system   kube-controller-manager-hp-tw-01          1/1     Running             0          45m
kube-system   kube-proxy-25xmk                          0/1     ContainerCreating   0          37m
kube-system   kube-proxy-4q728                          1/1     Running             0          44m
kube-system   kube-scheduler-hp-tw-01                   1/1     Running             0          45m

thomas.bucaioni

Anyway, for the training, maybe I can run everything from the cp node without worker?

thomas.bucaioni

Finally, I created two instances at AWS, but the join command gets stuck:

$ kubeadm join k8scp:6443 --token jlb7a6.azs6ad1ocv7nuh75 --discovery-token-ca-cert-hash sha256:0f00ba05e423ad5d51cb18343b9a97c0b0cd73b81ab5a948ee2208d1051085d5 --v=5
I0417 14:30:10.929810   31767 join.go:405] [preflight] found NodeName empty; using OS hostname as NodeName
I0417 14:30:10.930110   31767 initconfiguration.go:116] detected and using CRI socket: /var/run/dockershim.sock
[preflight] Running pre-flight checks
I0417 14:30:10.930376   31767 preflight.go:92] [preflight] Running general checks
I0417 14:30:10.930539   31767 checks.go:245] validating the existence and emptiness of directory /etc/kubernetes/manifests
I0417 14:30:10.930680   31767 checks.go:282] validating the existence of file /etc/kubernetes/kubelet.conf
I0417 14:30:10.930745   31767 checks.go:282] validating the existence of file /etc/kubernetes/bootstrap-kubelet.conf
I0417 14:30:10.930831   31767 checks.go:106] validating the container runtime
I0417 14:30:10.983222   31767 checks.go:132] validating if the "docker" service is enabled and active
I0417 14:30:10.998636   31767 checks.go:331] validating the contents of file /proc/sys/net/bridge/bridge-nf-call-iptables
I0417 14:30:10.998725   31767 checks.go:331] validating the contents of file /proc/sys/net/ipv4/ip_forward
I0417 14:30:10.998790   31767 checks.go:649] validating whether swap is enabled or not
I0417 14:30:10.998856   31767 checks.go:372] validating the presence of executable conntrack
I0417 14:30:10.998909   31767 checks.go:372] validating the presence of executable ip
I0417 14:30:10.998964   31767 checks.go:372] validating the presence of executable iptables
I0417 14:30:10.999005   31767 checks.go:372] validating the presence of executable mount
I0417 14:30:10.999054   31767 checks.go:372] validating the presence of executable nsenter
I0417 14:30:10.999102   31767 checks.go:372] validating the presence of executable ebtables
I0417 14:30:10.999141   31767 checks.go:372] validating the presence of executable ethtool
I0417 14:30:10.999199   31767 checks.go:372] validating the presence of executable socat
I0417 14:30:10.999263   31767 checks.go:372] validating the presence of executable tc
I0417 14:30:10.999311   31767 checks.go:372] validating the presence of executable touch
I0417 14:30:10.999376   31767 checks.go:520] running all checks
I0417 14:30:11.054823   31767 checks.go:403] checking whether the given node name is valid and reachable using net.LookupHost
I0417 14:30:11.057728   31767 checks.go:618] validating kubelet version
I0417 14:30:11.137518   31767 checks.go:132] validating if the "kubelet" service is enabled and active
I0417 14:30:11.148454   31767 checks.go:205] validating availability of port 10250
I0417 14:30:11.148620   31767 checks.go:282] validating the existence of file /etc/kubernetes/pki/ca.crt
I0417 14:30:11.148651   31767 checks.go:432] validating if the connectivity type is via proxy or direct
I0417 14:30:11.148703   31767 join.go:475] [preflight] Discovering cluster-info
I0417 14:30:11.148756   31767 token.go:80] [discovery] Created cluster-info discovery client, requesting info from "k8scp:6443"
I0417 14:30:21.149488   31767 token.go:217] [discovery] Failed to request cluster-info, will try again: Get "https://k8scp:6443/api/v1/namespaces/kube-public/configmaps/cluster-info?timeout=10s": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
I0417 14:30:37.057291   31767 token.go:217] [discovery] Failed to request cluster-info, will try again: Get "https://k8scp:6443/api/v1/namespaces/kube-public/configmaps/cluster-info?timeout=10s": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
 

Any idea what goes wrong?

thomas.bucaioni

So after setting the security group to accept everything, the worker node managed to join. But the cp node says:

# kubectl get nodes
The connection to the server localhost:8080 was refused - did you specify the right host or port?

thomas.bucaioni

Calico was not running, everything is fine

chrispokorni

Hi @thomas.bucaioni,

In summary, when calico is not running then the cluster is not behaving as expected either. Calico is responsible for managing the pod network, which impacts some of the control plane pods also.

The IP subnets should be distinct in a cluster, meaning that the pod network (calico's default 192.168.0.0/16), the node network, and eventually the services network (cluster's default 10.96.0.0/12) should not overlap. In local environments it is typical to see the pod and node networks overlap, because many private networks use the 192.168.0.0/x default subnet. This causes issues because all these IP addresses are entered into iptables, where the cluster cannot tell the difference when an IP address represents a pod and when a node.

The k8scp entry is intended to be an alias only, not a hostname. It will help with chapter 16 on HA. You can build your cluster without the alias, but then ch 16 will require a fresh rebuild, assuming that the instructions from ch 3 are followed as presented.

For AWS-EC2 and GCP-GCE infrastructures, you can find video guides for each environment's configuration, where VPC's and firewalls/GCs considerations are discussed as well.

Regards,
-Chris

thomas.bucaioni

So, in AWS everything goes well: tcpdump, the load balancer, and even the access from outside the cluster. Fixed

thomas.bucaioni

Hi @chrispokorni,
Just saw your answer. Indeed, the reason it didn't work on my baremetal Pcs must be the overlap of Ip ranges... Thanks for confirming
The cluster is ready for chapter 16 then, no worries.
Starting back at chapter 1, I saw the videos and I gave it a try at Aws. Everything is clear, it works just perfect now
Cheers,
Thomas